WO2000/02846 discloses a process for preparing a phenoxyacetic acid derivative represented by general formula (X), which comprises the step of treating an amine of formula (IX):
with an alkylating agent represented by general formula (XI):
wherein R4 is a lower alkoxy group, R5 and R6 are a lower alkyl group, Y is an eliminating group such as a p-toluenesulfonyloxy or methanesulfonyl group, a chlorine, bromine or iodine atom and the like, in the presence or absence of a base. However, WO2000/02846 does not teach or suggest a compound represented by general formula (I) of the present invention.